Documentation/thinkpad-acpi.txt

		     ThinkPad ACPI Extras Driver

                            Version 0.18
                         October 08th, 2007

               Borislav Deianov <borislav@users.sf.net>
             Henrique de Moraes Holschuh <hmh@hmh.eng.br>
                      http://ibm-acpi.sf.net/


This is a Linux driver for the IBM and Lenovo ThinkPad laptops. It
supports various features of these laptops which are accessible
through the ACPI and ACPI EC framework, but not otherwise fully
supported by the generic Linux ACPI drivers.

This driver used to be named ibm-acpi until kernel 2.6.21 and release
0.13-20070314.  It used to be in the drivers/acpi tree, but it was
moved to the drivers/misc tree and renamed to thinkpad-acpi for kernel
2.6.22, and release 0.14.


Status
------

The features currently supported are the following (see below for
detailed description):

	- Fn key combinations
	- Bluetooth enable and disable
	- video output switching, expansion control
	- ThinkLight on and off
	- limited docking and undocking
	- UltraBay eject
	- CMOS control
	- LED control
	- ACPI sounds
	- temperature sensors
	- Experimental: embedded controller register dump
	- LCD brightness control
	- Volume control
	- Fan control and monitoring: fan speed, fan enable/disable
	- Experimental: WAN enable and disable

A compatibility table by model and feature is maintained on the web
site, http://ibm-acpi.sf.net/. I appreciate any success or failure
reports, especially if they add to or correct the compatibility table.
Please include the following information in your report:

	- ThinkPad model name
	- a copy of your DSDT, from /proc/acpi/dsdt
	- a copy of the output of dmidecode, with serial numbers
	  and UUIDs masked off
	- which driver features work and which don't
	- the observed behavior of non-working features

Any other comments or patches are also more than welcome.


Installation
------------

If you are compiling this driver as included in the Linux kernel
sources, simply enable the CONFIG_THINKPAD_ACPI option, and optionally
enable the CONFIG_THINKPAD_ACPI_BAY option if you want the
thinkpad-specific bay functionality.

Features
--------

The driver exports two different interfaces to userspace, which can be
used to access the features it provides.  One is a legacy procfs-based
interface, which will be removed at some time in the distant future.
The other is a new sysfs-based interface which is not complete yet.

The procfs interface creates the /proc/acpi/ibm directory.  There is a
file under that directory for each feature it supports.  The procfs
interface is mostly frozen, and will change very little if at all: it
will not be extended to add any new functionality in the driver, instead
all new functionality will be implemented on the sysfs interface.

The sysfs interface tries to blend in the generic Linux sysfs subsystems
and classes as much as possible.  Since some of these subsystems are not
yet ready or stabilized, it is expected that this interface will change,
and any and all userspace programs must deal with it.


Notes about the sysfs interface:

Unlike what was done with the procfs interface, correctness when talking
to the sysfs interfaces will be enforced, as will correctness in the
thinkpad-acpi's implementation of sysfs interfaces.

Also, any bugs in the thinkpad-acpi sysfs driver code or in the
thinkpad-acpi's implementation of the sysfs interfaces will be fixed for
maximum correctness, even if that means changing an interface in
non-compatible ways.  As these interfaces mature both in the kernel and
in thinkpad-acpi, such changes should become quite rare.

Applications interfacing to the thinkpad-acpi sysfs interfaces must
follow all sysfs guidelines and correctly process all errors (the sysfs
interface makes extensive use of errors).  File descriptors and open /
close operations to the sysfs inodes must also be properly implemented.

The version of thinkpad-acpi's sysfs interface is exported by the driver
as a driver attribute (see below).

Sysfs driver attributes are on the driver's sysfs attribute space,
for 2.6.23 this is /sys/bus/platform/drivers/thinkpad_acpi/ and
/sys/bus/platform/drivers/thinkpad_hwmon/

Sysfs device attributes are on the thinkpad_acpi device sysfs attribute
space, for 2.6.23 this is /sys/devices/platform/thinkpad_acpi/.

Sysfs device attributes for the sensors and fan are on the
thinkpad_hwmon device's sysfs attribute space, but you should locate it
looking for a hwmon device with the name attribute of "thinkpad".

Driver version
--------------

procfs: /proc/acpi/ibm/driver
sysfs driver attribute: version

The driver name and version. No commands can be written to this file.

Sysfs interface version
-----------------------

sysfs driver attribute: interface_version

Version of the thinkpad-acpi sysfs interface, as an unsigned long
(output in hex format: 0xAAAABBCC), where:
	AAAA - major revision
	BB - minor revision
	CC - bugfix revision

The sysfs interface version changelog for the driver can be found at the
end of this document.  Changes to the sysfs interface done by the kernel
subsystems are not documented here, nor are they tracked by this
attribute.

Changes to the thinkpad-acpi sysfs interface are only considered
non-experimental when they are submitted to Linux mainline, at which
point the changes in this interface are documented and interface_version
may be updated.  If you are using any thinkpad-acpi features not yet
sent to mainline for merging, you do so on your own risk: these features
may disappear, or be implemented in a different and incompatible way by
the time they are merged in Linux mainline.

Changes that are backwards-compatible by nature (e.g. the addition of
attributes that do not change the way the other attributes work) do not
always warrant an update of interface_version.  Therefore, one must
expect that an attribute might not be there, and deal with it properly
(an attribute not being there *is* a valid way to make it clear that a
feature is not available in sysfs).

Hot keys
--------

procfs: /proc/acpi/ibm/hotkey
sysfs device attribute: hotkey_*

In a ThinkPad, the ACPI HKEY handler is responsible for comunicating
some important events and also keyboard hot key presses to the operating
system.  Enabling the hotkey functionality of thinkpad-acpi signals the
firmware that such a driver is present, and modifies how the ThinkPad
firmware will behave in many situations.

The driver enables the hot key feature automatically when loaded.  The
feature can later be disabled and enabled back at runtime.  The driver
will also restore the hot key feature to its previous state and mask
when it is unloaded.

When the hotkey feature is enabled and the hot key mask is set (see
below), the driver will report HKEY events in the following format:

	ibm/hotkey HKEY 00000080 0000xxxx

Some of these events refer to hot key presses, but not all.

The driver will generate events over the input layer for hot keys and
radio switches, and over the ACPI netlink layer for other events.  The
input layer support accepts the standard IOCTLs to remap the keycodes
assigned to each hot key.

The hot key bit mask allows some control over which hot keys generate
events.  If a key is "masked" (bit set to 0 in the mask), the firmware
will handle it.  If it is "unmasked", it signals the firmware that
thinkpad-acpi would prefer to handle it, if the firmware would be so
kind to allow it (and it often doesn't!).

Not all bits in the mask can be modified.  Not all bits that can be
modified do anything.  Not all hot keys can be individually controlled
by the mask.  Some models do not support the mask at all, and in those
models, hot keys cannot be controlled individually.  The behaviour of
the mask is, therefore, higly dependent on the ThinkPad model.

Note that unmasking some keys prevents their default behavior.  For
example, if Fn+F5 is unmasked, that key will no longer enable/disable
Bluetooth by itself.

Note also that not all Fn key combinations are supported through ACPI.
For example, on the X40, the brightness, volume and "Access IBM" buttons
do not generate ACPI events even with this driver.  They *can* be used
through the "ThinkPad Buttons" utility, see http://www.nongnu.org/tpb/

procfs notes:

The following commands can be written to the /proc/acpi/ibm/hotkey file:

	echo enable > /proc/acpi/ibm/hotkey -- enable the hot keys feature
	echo disable > /proc/acpi/ibm/hotkey -- disable the hot keys feature
	echo 0xffffffff > /proc/acpi/ibm/hotkey -- enable all hot keys
	echo 0 > /proc/acpi/ibm/hotkey -- disable all possible hot keys
	... any other 8-hex-digit mask ...
	echo reset > /proc/acpi/ibm/hotkey -- restore the original mask

The procfs interface does not support NVRAM polling control.  So as to
maintain maximum bug-to-bug compatibility, it does not report any masks,
nor does it allow one to manipulate the hot key mask when the firmware
does not support masks at all, even if NVRAM polling is in use.

sysfs notes:

	hotkey_bios_enabled:
		Returns the status of the hot keys feature when
		thinkpad-acpi was loaded.  Upon module unload, the hot
		key feature status will be restored to this value.

		0: hot keys were disabled
		1: hot keys were enabled (unusual)

	hotkey_bios_mask:
		Returns the hot keys mask when thinkpad-acpi was loaded.
		Upon module unload, the hot keys mask will be restored
		to this value.

	hotkey_enable:
		Enables/disables the hot keys feature in the ACPI
		firmware, and reports current status of the hot keys
		feature.  Has no effect on the NVRAM hot key polling
		functionality.

		0: disables the hot keys feature / feature disabled
		1: enables the hot keys feature / feature enabled

	hotkey_mask:
		bit mask to enable driver-handling (and depending on
		the firmware, ACPI event generation) for each hot key
		(see above).  Returns the current status of the hot keys
		mask, and allows one to modify it.

		Note: when NVRAM polling is active, the firmware mask
		will be different from the value returned by
		hotkey_mask.  The driver will retain enabled bits for
		hotkeys that are under NVRAM polling even if the
		firmware refuses them, and will not set these bits on
		the firmware hot key mask.

	hotkey_all_mask:
		bit mask that should enable event reporting for all
		supported hot keys, when echoed to hotkey_mask above.
		Unless you know which events need to be handled
		passively (because the firmware *will* handle them
		anyway), do *not* use hotkey_all_mask.  Use
		hotkey_recommended_mask, instead. You have been warned.

	hotkey_recommended_mask:
		bit mask that should enable event reporting for all
		supported hot keys, except those which are always
		handled by the firmware anyway.  Echo it to
		hotkey_mask above, to use.

	hotkey_source_mask:
		bit mask that selects which hot keys will the driver
		poll the NVRAM for.  This is auto-detected by the driver
		based on the capabilities reported by the ACPI firmware,
		but it can be overridden at runtime.

		Hot keys whose bits are set in both hotkey_source_mask
		and also on hotkey_mask are polled for in NVRAM.  Only a
		few hot keys are available through CMOS NVRAM polling.

		Warning: when in NVRAM mode, the volume up/down/mute
		keys are synthesized according to changes in the mixer,
		so you have to use volume up or volume down to unmute,
		as per the ThinkPad volume mixer user interface.  When
		in ACPI event mode, volume up/down/mute are reported as
		separate events, but this behaviour may be corrected in
		future releases of this driver, in which case the
		ThinkPad volume mixer user interface semanthics will be
		enforced.

	hotkey_poll_freq:
		frequency in Hz for hot key polling. It must be between
		0 and 25 Hz.  Polling is only carried out when strictly
		needed.

		Setting hotkey_poll_freq to zero disables polling, and
		will cause hot key presses that require NVRAM polling
		to never be reported.

		Setting hotkey_poll_freq too low will cause repeated
		pressings of the same hot key to be misreported as a
		single key press, or to not even be detected at all.
		The recommended polling frequency is 10Hz.

	hotkey_radio_sw:
		if the ThinkPad has a hardware radio switch, this
		attribute will read 0 if the switch is in the "radios
		disabled" postition, and 1 if the switch is in the
		"radios enabled" position.

	hotkey_report_mode:
		Returns the state of the procfs ACPI event report mode
		filter for hot keys.  If it is set to 1 (the default),
		all hot key presses are reported both through the input
		layer and also as ACPI events through procfs (but not
		through netlink).  If it is set to 2, hot key presses
		are reported only through the input layer.

		This attribute is read-only in kernels 2.6.23 or later,
		and read-write on earlier kernels.

		May return -EPERM (write access locked out by module
		parameter) or -EACCES (read-only).

	wakeup_reason:
		Set to 1 if the system is waking up because the user
		requested a bay ejection.  Set to 2 if the system is
		waking up because the user requested the system to
		undock.  Set to zero for normal wake-ups or wake-ups
		due to unknown reasons.

	wakeup_hotunplug_complete:
		Set to 1 if the system was waken up because of an
		undock or bay ejection request, and that request
		was sucessfully completed.  At this point, it might
		be useful to send the system back to sleep, at the
		user's choice.  Refer to HKEY events 0x4003 and
		0x3003, below.

input layer notes:

A Hot key is mapped to a single input layer EV_KEY event, possibly
followed by an EV_MSC MSC_SCAN event that shall contain that key's scan
code.  An EV_SYN event will always be generated to mark the end of the
event block.

Do not use the EV_MSC MSC_SCAN events to process keys.  They are to be
used as a helper to remap keys, only.  They are particularly useful when
remapping KEY_UNKNOWN keys.

The events are available in an input device, with the following id:

	Bus:		BUS_HOST
	vendor:		0x1014 (PCI_VENDOR_ID_IBM)  or
			0x17aa (PCI_VENDOR_ID_LENOVO)
	product:	0x5054 ("TP")
	version:	0x4101

The version will have its LSB incremented if the keymap changes in a
backwards-compatible way.  The MSB shall always be 0x41 for this input
device.  If the MSB is not 0x41, do not use the device as described in
this section, as it is either something else (e.g. another input device
exported by a thinkpad driver, such as HDAPS) or its functionality has
been changed in a non-backwards compatible way.

Adding other event types for other functionalities shall be considered a
backwards-compatible change for this input device.

Thinkpad-acpi Hot Key event map (version 0x4101):

ACPI	Scan
event	code	Key		Notes

0x1001	0x00	FN+F1		-
0x1002	0x01	FN+F2		IBM: battery (rare)
				Lenovo: Screen lock

0x1003	0x02	FN+F3		Many IBM models always report
				this hot key, even with hot keys
				disabled or with Fn+F3 masked
				off
				IBM: screen lock
				Lenovo: battery

0x1004	0x03	FN+F4		Sleep button (ACPI sleep button
				semanthics, i.e. sleep-to-RAM).
				It is always generate some kind
				of event, either the hot key
				event or a ACPI sleep button
				event. The firmware may
				refuse to generate further FN+F4
				key presses until a S3 or S4 ACPI
				sleep cycle is performed or some
				time passes.

0x1005	0x04	FN+F5		Radio.  Enables/disables
				the internal BlueTooth hardware
				and W-WAN card if left in control
				of the firmware.  Does not affect
				the WLAN card.
				Should be used to turn on/off all
				radios (bluetooth+W-WAN+WLAN),
				really.

0x1006	0x05	FN+F6		-

0x1007	0x06	FN+F7		Video output cycle.
				Do you feel lucky today?

0x1008	0x07	FN+F8		IBM: toggle screen expand
				Lenovo: configure ultranav

0x1009	0x08	FN+F9		-
	..	..		..
0x100B	0x0A	FN+F11		-

0x100C	0x0B	FN+F12		Sleep to disk.  You are always
				supposed to handle it yourself,
				either through the ACPI event,
				or through a hotkey event.
				The firmware may refuse to
				generate further FN+F4 key
				press events until a S3 or S4
				ACPI sleep cycle is performed,
				or some time passes.

0x100D	0x0C	FN+BACKSPACE	-
0x100E	0x0D	FN+INSERT	-
0x100F	0x0E	FN+DELETE	-

0x1010	0x0F	FN+HOME		Brightness up.  This key is
				always handled by the firmware
				in IBM ThinkPads, even when
				unmasked.  Just leave it alone.
				For Lenovo ThinkPads with a new
				BIOS, it has to be handled either
				by the ACPI OSI, or by userspace.
0x1011	0x10	FN+END		Brightness down.  See brightness
				up for details.

0x1012	0x11	FN+PGUP		Thinklight toggle.  This key is
				always handled by the firmware,
				even when unmasked.

0x1013	0x12	FN+PGDOWN	-

0x1014	0x13	FN+SPACE	Zoom key

0x1015	0x14	VOLUME UP	Internal mixer volume up. This
				key is always handled by the
				firmware, even when unmasked.
				NOTE: Lenovo seems to be changing
				this.
0x1016	0x15	VOLUME DOWN	Internal mixer volume up. This
				key is always handled by the
				firmware, even when unmasked.
				NOTE: Lenovo seems to be changing
				this.
0x1017	0x16	MUTE		Mute internal mixer. This
				key is always handled by the
				firmware, even when unmasked.

0x1018	0x17	THINKPAD	Thinkpad/Access IBM/Lenovo key

0x1019	0x18	unknown
..	..	..
0x1020	0x1F	unknown

The ThinkPad firmware does not allow one to differentiate when most hot
keys are pressed or released (either that, or we don't know how to, yet).
For these keys, the driver generates a set of events for a key press and
immediately issues the same set of events for a key release.  It is
unknown by the driver if the ThinkPad firmware triggered these events on
hot key press or release, but the firmware will do it for either one, not
both.

If a key is mapped to KEY_RESERVED, it generates no input events at all.
If a key is mapped to KEY_UNKNOWN, it generates an input event that
includes an scan code.  If a key is mapped to anything else, it will
generate input device EV_KEY events.

Non hot-key ACPI HKEY event map:
0x5001		Lid closed
0x5002		Lid opened
0x7000		Radio Switch may have changed state

The above events are not propagated by the driver, except for legacy
compatibility purposes when hotkey_report_mode is set to 1.

0x2304		System is waking up from suspend to undock
0x2305		System is waking up from suspend to eject bay
0x2404		System is waking up from hibernation to undock
0x2405		System is waking up from hibernation to eject bay

The above events are never propagated by the driver.

0x3003		Bay ejection (see 0x2x05) complete, can sleep again
0x4003		Undocked (see 0x2x04), can sleep again
0x5010		Brightness level changed (newer Lenovo BIOSes)

The above events are propagated by the driver.

Compatibility notes:

ibm-acpi and thinkpad-acpi 0.15 (mainline kernels before 2.6.23) never
supported the input layer, and sent events over the procfs ACPI event
interface.

To avoid sending duplicate events over the input layer and the ACPI
event interface, thinkpad-acpi 0.16 implements a module parameter
(hotkey_report_mode), and also a sysfs device attribute with the same
name.

Make no mistake here: userspace is expected to switch to using the input
layer interface of thinkpad-acpi, together with the ACPI netlink event
interface in kernels 2.6.23 and later, or with the ACPI procfs event
interface in kernels 2.6.22 and earlier.

If no hotkey_report_mode module parameter is specified (or it is set to
zero), the driver defaults to mode 1 (see below), and on kernels 2.6.22
and earlier, also allows one to change the hotkey_report_mode through
sysfs.  In kernels 2.6.23 and later, where the netlink ACPI event
interface is available, hotkey_report_mode cannot be changed through
sysfs (it is read-only).

If the hotkey_report_mode module parameter is set to 1 or 2, it cannot
be changed later through sysfs (any writes will return -EPERM to signal
that hotkey_report_mode was locked.  On 2.6.23 and later, where
hotkey_report_mode cannot be changed at all, writes will return -EACES).

hotkey_report_mode set to 1 makes the driver export through the procfs
ACPI event interface all hot key presses (which are *also* sent to the
input layer).  This is a legacy compatibility behaviour, and it is also
the default mode of operation for the driver.

hotkey_report_mode set to 2 makes the driver filter out the hot key
presses from the procfs ACPI event interface, so these events will only
be sent through the input layer.  Userspace that has been updated to use
the thinkpad-acpi input layer interface should set hotkey_report_mode to
2.

Hot key press events are never sent to the ACPI netlink event interface.
Really up-to-date userspace under kernel 2.6.23 and later is to use the
netlink interface and the input layer interface, and don't bother at all
with hotkey_report_mode.


Bluetooth
---------

procfs: /proc/acpi/ibm/bluetooth
sysfs device attribute: bluetooth_enable

This feature shows the presence and current state of a ThinkPad
Bluetooth device in the internal ThinkPad CDC slot.

Procfs notes:

If Bluetooth is installed, the following commands can be used:

	echo enable > /proc/acpi/ibm/bluetooth
	echo disable > /proc/acpi/ibm/bluetooth

Sysfs notes:

	If the Bluetooth CDC card is installed, it can be enabled /
	disabled through the "bluetooth_enable" thinkpad-acpi device
	attribute, and its current status can also be queried.

	enable:
		0: disables Bluetooth / Bluetooth is disabled
		1: enables Bluetooth / Bluetooth is enabled.

	Note: this interface will be probably be superseeded by the
	generic rfkill class, so it is NOT to be considered stable yet.

Video output control -- /proc/acpi/ibm/video
--------------------------------------------

This feature allows control over the devices used for video output -
LCD, CRT or DVI (if available). The following commands are available:

	echo lcd_enable > /proc/acpi/ibm/video
	echo lcd_disable > /proc/acpi/ibm/video
	echo crt_enable > /proc/acpi/ibm/video
	echo crt_disable > /proc/acpi/ibm/video
	echo dvi_enable > /proc/acpi/ibm/video
	echo dvi_disable > /proc/acpi/ibm/video
	echo auto_enable > /proc/acpi/ibm/video
	echo auto_disable > /proc/acpi/ibm/video
	echo expand_toggle > /proc/acpi/ibm/video
	echo video_switch > /proc/acpi/ibm/video

Each video output device can be enabled or disabled individually.
Reading /proc/acpi/ibm/video shows the status of each device.

Automatic video switching can be enabled or disabled.  When automatic
video switching is enabled, certain events (e.g. opening the lid,
docking or undocking) cause the video output device to change
automatically. While this can be useful, it also causes flickering
and, on the X40, video corruption. By disabling automatic switching,
the flickering or video corruption can be avoided.

The video_switch command cycles through the available video outputs
(it simulates the behavior of Fn-F7).

Video expansion can be toggled through this feature. This controls
whether the display is expanded to fill the entire LCD screen when a
mode with less than full resolution is used. Note that the current
video expansion status cannot be determined through this feature.

Note that on many models (particularly those using Radeon graphics
chips) the X driver configures the video card in a way which prevents
Fn-F7 from working. This also disables the video output switching
features of this driver, as it uses the same ACPI methods as
Fn-F7. Video switching on the console should still work.

UPDATE: There's now a patch for the X.org Radeon driver which
addresses this issue. Some people are reporting success with the patch
while others are still having problems. For more information:

https://bugs.freedesktop.org/show_bug.cgi?id=2000

ThinkLight control -- /proc/acpi/ibm/light
------------------------------------------

The current status of the ThinkLight can be found in this file. A few
models which do not make the status available will show it as
"unknown". The available commands are:

	echo on  > /proc/acpi/ibm/light
	echo off > /proc/acpi/ibm/light

Docking / undocking -- /proc/acpi/ibm/dock
------------------------------------------

Docking and undocking (e.g. with the X4 UltraBase) requires some
actions to be taken by the operating system to safely make or break
the electrical connections with the dock.

The docking feature of this driver generates the following ACPI events:

	ibm/dock GDCK 00000003 00000001 -- eject request
	ibm/dock GDCK 00000003 00000002 -- undocked
	ibm/dock GDCK 00000000 00000003 -- docked

NOTE: These events will only be generated if the laptop was docked
when originally booted. This is due to the current lack of support for
hot plugging of devices in the Linux ACPI framework. If the laptop was
booted while not in the dock, the following message is shown in the
logs:

	Mar 17 01:42:34 aero kernel: thinkpad_acpi: dock device not present

In this case, no dock-related events are generated but the dock and
undock commands described below still work. They can be executed
manually or triggered by Fn key combinations (see the example acpid
configuration files included in the driver tarball package available
on the web site).

When the eject request button on the dock is pressed, the first event
above is generated. The handler for this event should issue the
following command:

	echo undock > /proc/acpi/ibm/dock

After the LED on the dock goes off, it is safe to eject the laptop.
Note: if you pressed this key by mistake, go ahead and eject the
laptop, then dock it back in. Otherwise, the dock may not function as
expected.

When the laptop is docked, the third event above is generated. The
handler for this event should issue the following command to fully
enable the dock:

	echo dock > /proc/acpi/ibm/dock

The contents of the /proc/acpi/ibm/dock file shows the current status
of the dock, as provided by the ACPI framework.

The docking support in this driver does not take care of enabling or
disabling any other devices you may have attached to the dock. For
example, a CD drive plugged into the UltraBase needs to be disabled or
enabled separately. See the provided example acpid configuration files
for how this can be accomplished.

There is no support yet for PCI devices that may be attached to a
docking station, e.g. in the ThinkPad Dock II. The driver currently
does not recognize, enable or disable such devices. This means that
the only docking stations currently supported are the X-series
UltraBase docks and "dumb" port replicators like the Mini Dock (the
latter don't need any ACPI support, actually).

UltraBay eject -- /proc/acpi/ibm/bay
------------------------------------

Inserting or ejecting an UltraBay device requires some actions to be
taken by the operating system to safely make or break the electrical
connections with the device.

This feature generates the following ACPI events:

	ibm/bay MSTR 00000003 00000000 -- eject request
	ibm/bay MSTR 00000001 00000000 -- eject lever inserted

NOTE: These events will only be generated if the UltraBay was present
when the laptop was originally booted (on the X series, the UltraBay
is in the dock, so it may not be present if the laptop was undocked).
This is due to the current lack of support for hot plugging of devices
in the Linux ACPI framework. If the laptop was booted without the
UltraBay, the following message is shown in the logs:

	Mar 17 01:42:34 aero kernel: thinkpad_acpi: bay device not present

In this case, no bay-related events are generated but the eject
command described below still works. It can be executed manually or
triggered by a hot key combination.

Sliding the eject lever generates the first event shown above. The
handler for this event should take whatever actions are necessary to
shut down the device in the UltraBay (e.g. call idectl), then issue
the following command:

	echo eject > /proc/acpi/ibm/bay

After the LED on the UltraBay goes off, it is safe to pull out the
device.

When the eject lever is inserted, the second event above is
generated. The handler for this event should take whatever actions are
necessary to enable the UltraBay device (e.g. call idectl).

The contents of the /proc/acpi/ibm/bay file shows the current status
of the UltraBay, as provided by the ACPI framework.

EXPERIMENTAL warm eject support on the 600e/x, A22p and A3x (To use
this feature, you need to supply the experimental=1 parameter when
loading the module):

These models do not have a button near the UltraBay device to request
a hot eject but rather require the laptop to be put to sleep
(suspend-to-ram) before the bay device is ejected or inserted).
The sequence of steps to eject the device is as follows:

	echo eject > /proc/acpi/ibm/bay
	put the ThinkPad to sleep
	remove the drive
	resume from sleep
	cat /proc/acpi/ibm/bay should show that the drive was removed

On the A3x, both the UltraBay 2000 and UltraBay Plus devices are
supported. Use "eject2" instead of "eject" for the second bay.

Note: the UltraBay eject support on the 600e/x, A22p and A3x is
EXPERIMENTAL and may not work as expected. USE WITH CAUTION!

CMOS control
------------

procfs: /proc/acpi/ibm/cmos
sysfs device attribute: cmos_command

This feature is mostly used internally by the ACPI firmware to keep the legacy
CMOS NVRAM bits in sync with the current machine state, and to record this
state so that the ThinkPad will retain such settings across reboots.

Some of these commands actually perform actions in some ThinkPad models, but
this is expected to disappear more and more in newer models.  As an example, in
a T43 and in a X40, commands 12 and 13 still control the ThinkLight state for
real, but commands 0 to 2 don't control the mixer anymore (they have been
phased out) and just update the NVRAM.

The range of valid cmos command numbers is 0 to 21, but not all have an
effect and the behavior varies from model to model.  Here is the behavior
on the X40 (tpb is the ThinkPad Buttons utility):

	0 - Related to "Volume down" key press
	1 - Related to "Volume up" key press
	2 - Related to "Mute on" key press
	3 - Related to "Access IBM" key press
	4 - Related to "LCD brightness up" key pess
	5 - Related to "LCD brightness down" key press
	11 - Related to "toggle screen expansion" key press/function
	12 - Related to "ThinkLight on"
	13 - Related to "ThinkLight off"
	14 - Related to "ThinkLight" key press (toggle thinklight)

The cmos command interface is prone to firmware split-brain problems, as
in newer ThinkPads it is just a compatibility layer.  Do not use it, it is
exported just as a debug tool.

LED control -- /proc/acpi/ibm/led
---------------------------------

Some of the LED indicators can be controlled through this feature. The
available commands are:

	echo '<led number> on' >/proc/acpi/ibm/led
	echo '<led number> off' >/proc/acpi/ibm/led
	echo '<led number> blink' >/proc/acpi/ibm/led

The <led number> range is 0 to 7. The set of LEDs that can be
controlled varies from model to model. Here is the mapping on the X40:

	0 - power
	1 - battery (orange)
	2 - battery (green)
	3 - UltraBase
	4 - UltraBay
	7 - standby

All of the above can be turned on and off and can be made to blink.

ACPI sounds -- /proc/acpi/ibm/beep
----------------------------------

The BEEP method is used internally by the ACPI firmware to provide
audible alerts in various situations. This feature allows the same
sounds to be triggered manually.

The commands are non-negative integer numbers:

	echo <number> >/proc/acpi/ibm/beep

The valid <number> range is 0 to 17. Not all numbers trigger sounds
and the sounds vary from model to model. Here is the behavior on the
X40:

	0 - stop a sound in progress (but use 17 to stop 16)
	2 - two beeps, pause, third beep ("low battery")
	3 - single beep
	4 - high, followed by low-pitched beep ("unable")
	5 - single beep
	6 - very high, followed by high-pitched beep ("AC/DC")
	7 - high-pitched beep
	9 - three short beeps
	10 - very long beep
	12 - low-pitched beep
	15 - three high-pitched beeps repeating constantly, stop with 0
	16 - one medium-pitched beep repeating constantly, stop with 17
	17 - stop 16

Temperature sensors
-------------------

procfs: /proc/acpi/ibm/thermal
sysfs device attributes: (hwmon "thinkpad") temp*_input

Most ThinkPads include six or more separate temperature sensors but only
expose the CPU temperature through the standard ACPI methods.  This
feature shows readings from up to eight different sensors on older
ThinkPads, and up to sixteen different sensors on newer ThinkPads.

For example, on the X40, a typical output may be:
temperatures:   42 42 45 41 36 -128 33 -128

On the T43/p, a typical output may be:
temperatures:   48 48 36 52 38 -128 31 -128 48 52 48 -128 -128 -128 -128 -128

The mapping of thermal sensors to physical locations varies depending on
system-board model (and thus, on ThinkPad model).

http://thinkwiki.org/wiki/Thermal_Sensors is a public wiki page that
tries to track down these locations for various models.

Most (newer?) models seem to follow this pattern:

1:  CPU
2:  (depends on model)
3:  (depends on model)
4:  GPU
5:  Main battery: main sensor
6:  Bay battery: main sensor
7:  Main battery: secondary sensor
8:  Bay battery: secondary sensor
9-15: (depends on model)

For the R51 (source: Thomas Gruber):
2:  Mini-PCI
3:  Internal HDD

For the T43, T43/p (source: Shmidoax/Thinkwiki.org)
http://thinkwiki.org/wiki/Thermal_Sensors#ThinkPad_T43.2C_T43p
2:  System board, left side (near PCMCIA slot), reported as HDAPS temp
3:  PCMCIA slot
9:  MCH (northbridge) to DRAM Bus
10: Clock-generator, mini-pci card and ICH (southbridge), under Mini-PCI
    card, under touchpad
11: Power regulator, underside of system board, below F2 key

The A31 has a very atypical layout for the thermal sensors
(source: Milos Popovic, http://thinkwiki.org/wiki/Thermal_Sensors#ThinkPad_A31)
1:  CPU
2:  Main Battery: main sensor
3:  Power Converter
4:  Bay Battery: main sensor
5:  MCH (northbridge)
6:  PCMCIA/ambient
7:  Main Battery: secondary sensor
8:  Bay Battery: secondary sensor


Procfs notes:
	Readings from sensors that are not available return -128.
	No commands can be written to this file.

Sysfs notes:
	Sensors that are not available return the ENXIO error.  This
	status may change at runtime, as there are hotplug thermal
	sensors, like those inside the batteries and docks.

	thinkpad-acpi thermal sensors are reported through the hwmon
	subsystem, and follow all of the hwmon guidelines at
	Documentation/hwmon.


EXPERIMENTAL: Embedded controller register dump -- /proc/acpi/ibm/ecdump
------------------------------------------------------------------------

This feature is marked EXPERIMENTAL because the implementation
directly accesses hardware registers and may not work as expected. USE
WITH CAUTION! To use this feature, you need to supply the
experimental=1 parameter when loading the module.

This feature dumps the values of 256 embedded controller
registers. Values which have changed since the last time the registers
were dumped are marked with a star:

[root@x40 ibm-acpi]# cat /proc/acpi/ibm/ecdump
EC       +00 +01 +02 +03 +04 +05 +06 +07 +08 +09 +0a +0b +0c +0d +0e +0f
EC 0x00:  a7  47  87  01  fe  96  00  08  01  00  cb  00  00  00  40  00
EC 0x10:  00  00  ff  ff  f4  3c  87  09  01  ff  42  01  ff  ff  0d  00
EC 0x20:  00  00  00  00  00  00  00  00  00  00  00  03  43  00  00  80
EC 0x30:  01  07  1a  00  30  04  00  00 *85  00  00  10  00  50  00  00
EC 0x40:  00  00  00  00  00  00  14  01  00  04  00  00  00  00  00  00
EC 0x50:  00  c0  02  0d  00  01  01  02  02  03  03  03  03 *bc *02 *bc
EC 0x60: *02 *bc *02  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0x70:  00  00  00  00  00  12  30  40 *24 *26 *2c *27 *20  80 *1f  80
EC 0x80:  00  00  00  06 *37 *0e  03  00  00  00  0e  07  00  00  00  00
EC 0x90:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xa0: *ff  09  ff  09  ff  ff *64  00 *00 *00 *a2  41 *ff *ff *e0  00
EC 0xb0:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xc0:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xd0:  03  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xe0:  00  00  00  00  00  00  00  00  11  20  49  04  24  06  55  03
EC 0xf0:  31  55  48  54  35  38  57  57  08  2f  45  73  07  65  6c  1a

This feature can be used to determine the register holding the fan
speed on some models. To do that, do the following:

	- make sure the battery is fully charged
	- make sure the fan is running
	- run 'cat /proc/acpi/ibm/ecdump' several times, once per second or so

The first step makes sure various charging-related values don't
vary. The second ensures that the fan-related values do vary, since
the fan speed fluctuates a bit. The third will (hopefully) mark the
fan register with a star:

[root@x40 ibm-acpi]# cat /proc/acpi/ibm/ecdump
EC       +00 +01 +02 +03 +04 +05 +06 +07 +08 +09 +0a +0b +0c +0d +0e +0f
EC 0x00:  a7  47  87  01  fe  96  00  08  01  00  cb  00  00  00  40  00
EC 0x10:  00  00  ff  ff  f4  3c  87  09  01  ff  42  01  ff  ff  0d  00
EC 0x20:  00  00  00  00  00  00  00  00  00  00  00  03  43  00  00  80
EC 0x30:  01  07  1a  00  30  04  00  00  85  00  00  10  00  50  00  00
EC 0x40:  00  00  00  00  00  00  14  01  00  04  00  00  00  00  00  00
EC 0x50:  00  c0  02  0d  00  01  01  02  02  03  03  03  03  bc  02  bc
EC 0x60:  02  bc  02  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0x70:  00  00  00  00  00  12  30  40  24  27  2c  27  21  80  1f  80
EC 0x80:  00  00  00  06 *be  0d  03  00  00  00  0e  07  00  00  00  00
EC 0x90:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xa0:  ff  09  ff  09  ff  ff  64  00  00  00  a2  41  ff  ff  e0  00
EC 0xb0:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xc0:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xd0:  03  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xe0:  00  00  00  00  00  00  00  00  11  20  49  04  24  06  55  03
EC 0xf0:  31  55  48  54  35  38  57  57  08  2f  45  73  07  65  6c  1a

Another set of values that varies often is the temperature
readings. Since temperatures don't change vary fast, you can take
several quick dumps to eliminate them.

You can use a similar method to figure out the meaning of other
embedded controller registers - e.g. make sure nothing else changes
except the charging or discharging battery to determine which
registers contain the current battery capacity, etc. If you experiment
with this, do send me your results (including some complete dumps with
a description of the conditions when they were taken.)

LCD brightness control
----------------------

procfs: /proc/acpi/ibm/brightness
sysfs backlight device "thinkpad_screen"

This feature allows software control of the LCD brightness on ThinkPad
models which don't have a hardware brightness slider.

It has some limitations: the LCD backlight cannot be actually turned on or
off by this interface, and in many ThinkPad models, the "dim while on
battery" functionality will be enabled by the BIOS when this interface is
used, and cannot be controlled.

On IBM (and some of the earlier Lenovo) ThinkPads, the backlight control
has eight brightness levels, ranging from 0 to 7.  Some of the levels
may not be distinct.  Later Lenovo models that implement the ACPI
display backlight brightness control methods have 16 levels, ranging
from 0 to 15.

There are two interfaces to the firmware for direct brightness control,
EC and CMOS.  To select which one should be used, use the
brightness_mode module parameter: brightness_mode=1 selects EC mode,
brightness_mode=2 selects CMOS mode, brightness_mode=3 selects both EC
and CMOS.  The driver tries to autodetect which interface to use.

When display backlight brightness controls are available through the
standard ACPI interface, it is best to use it instead of this direct
ThinkPad-specific interface.  The driver will disable its native
backlight brightness control interface if it detects that the standard
ACPI interface is available in the ThinkPad.

The brightness_enable module parameter can be used to control whether
the LCD brightness control feature will be enabled when available.
brightness_enable=0 forces it to be disabled.  brightness_enable=1
forces it to be enabled when available, even if the standard ACPI
interface is also available.

Procfs notes:

	The available commands are:

	echo up   >/proc/acpi/ibm/brightness
	echo down >/proc/acpi/ibm/brightness
	echo 'level <level>' >/proc/acpi/ibm/brightness

Sysfs notes:

The interface is implemented through the backlight sysfs class, which is
poorly documented at this time.

Locate the thinkpad_screen device under /sys/class/backlight, and inside
it there will be the following attributes:

	max_brightness:
		Reads the maximum brightness the hardware can be set to.
		The minimum is always zero.

	actual_brightness:
		Reads what brightness the screen is set to at this instant.

	brightness:
		Writes request the driver to change brightness to the
		given value.  Reads will tell you what brightness the
		driver is trying to set the display to when "power" is set
		to zero and the display has not been dimmed by a kernel
		power management event.

	power:
		power management mode, where 0 is "display on", and 1 to 3
		will dim the display backlight to brightness level 0
		because thinkpad-acpi cannot really turn the backlight
		off.  Kernel power management events can temporarily
		increase the current power management level, i.e. they can
		dim the display.


Volume control -- /proc/acpi/ibm/volume
---------------------------------------

This feature allows volume control on ThinkPad models which don't have
a hardware volume knob. The available commands are:

	echo up   >/proc/acpi/ibm/volume
	echo down >/proc/acpi/ibm/volume
	echo mute >/proc/acpi/ibm/volume
	echo 'level <level>' >/proc/acpi/ibm/volume

The <level> number range is 0 to 15 although not all of them may be
distinct. The unmute the volume after the mute command, use either the
up or down command (the level command will not unmute the volume).
The current volume level and mute state is shown in the file.

Fan control and monitoring: fan speed, fan enable/disable
---------------------------------------------------------

procfs: /proc/acpi/ibm/fan
sysfs device attributes: (hwmon "thinkpad") fan1_input, pwm1,
			  pwm1_enable
sysfs hwmon driver attributes: fan_watchdog

NOTE NOTE NOTE: fan control operations are disabled by default for
safety reasons.  To enable them, the module parameter "fan_control=1"
must be given to thinkpad-acpi.

This feature attempts to show the current fan speed, control mode and
other fan data that might be available.  The speed is read directly
from the hardware registers of the embedded controller.  This is known
to work on later R, T, X and Z series ThinkPads but may show a bogus
value on other models.

Fan levels:

Most ThinkPad fans work in "levels" at the firmware interface.  Level 0
stops the fan.  The higher the level, the higher the fan speed, although
adjacent levels often map to the same fan speed.  7 is the highest
level, where the fan reaches the maximum recommended speed.

Level "auto" means the EC changes the fan level according to some
internal algorithm, usually based on readings from the thermal sensors.

There is also a "full-speed" level, also known as "disengaged" level.
In this level, the EC disables the speed-locked closed-loop fan control,
and drives the fan as fast as it can go, which might exceed hardware
limits, so use this level with caution.

The fan usually ramps up or down slowly from one speed to another, and
it is normal for the EC to take several seconds to react to fan
commands.  The full-speed level may take up to two minutes to ramp up to
maximum speed, and in some ThinkPads, the tachometer readings go stale
while the EC is transitioning to the full-speed level.

WARNING WARNING WARNING: do not leave the fan disabled unless you are
monitoring all of the temperature sensor readings and you are ready to
enable it if necessary to avoid overheating.

An enabled fan in level "auto" may stop spinning if the EC decides the
ThinkPad is cool enough and doesn't need the extra airflow.  This is
normal, and the EC will spin the fan up if the various thermal readings
rise too much.

On the X40, this seems to depend on the CPU and HDD temperatures.
Specifically, the fan is turned on when either the CPU temperature
climbs to 56 degrees or the HDD temperature climbs to 46 degrees.  The
fan is turned off when the CPU temperature drops to 49 degrees and the
HDD temperature drops to 41 degrees.  These thresholds cannot
currently be controlled.

The ThinkPad's ACPI DSDT code will reprogram the fan on its own when
certain conditions are met.  It will override any fan programming done
through thinkpad-acpi.

The thinkpad-acpi kernel driver can be programmed to revert the fan
level to a safe setting if userspace does not issue one of the procfs
fan commands: "enable", "disable", "level" or "watchdog", or if there
are no writes to pwm1_enable (or to pwm1 *if and only if* pwm1_enable is
set to 1, manual mode) within a configurable amount of time of up to
120 seconds.  This functionality is called fan safety watchdog.

Note that the watchdog timer stops after it enables the fan.  It will be
rearmed again automatically (using the same interval) when one of the
above mentioned fan commands is received.  The fan watchdog is,
therefore, not suitable to protect against fan mode changes made through
means other than the "enable", "disable", and "level" procfs fan
commands, or the hwmon fan control sysfs interface.

Procfs notes:

The fan may be enabled or disabled with the following commands:

	echo enable  >/proc/acpi/ibm/fan
	echo disable >/proc/acpi/ibm/fan

Placing a fan on level 0 is the same as disabling it.  Enabling a fan
will try to place it in a safe level if it is too slow or disabled.

The fan level can be controlled with the command:

	echo 'level <level>' > /proc/acpi/ibm/fan

Where <level> is an integer from 0 to 7, or one of the words "auto" or
"full-speed" (without the quotes).  Not all ThinkPads support the "auto"
and "full-speed" levels.  The driver accepts "disengaged" as an alias for
"full-speed", and reports it as "disengaged" for backwards
compatibility.

On the X31 and X40 (and ONLY on those models), the fan speed can be
controlled to a certain degree.  Once the fan is running, it can be
forced to run faster or slower with the following command:

	echo 'speed <speed>' > /proc/acpi/ibm/fan

The sustainable range of fan speeds on the X40 appears to be from about
3700 to about 7350. Values outside this range either do not have any
effect or the fan speed eventually settles somewhere in that range.  The
fan cannot be stopped or started with this command.  This functionality
is incomplete, and not available through the sysfs interface.

To program the safety watchdog, use the "watchdog" command.

	echo 'watchdog <interval in seconds>' > /proc/acpi/ibm/fan

If you want to disable the watchdog, use 0 as the interval.

Sysfs notes:

The sysfs interface follows the hwmon subsystem guidelines for the most
part, and the exception is the fan safety watchdog.

Writes to any of the sysfs attributes may return the EINVAL error if
that operation is not supported in a given ThinkPad or if the parameter
is out-of-bounds, and EPERM if it is forbidden.  They may also return
EINTR (interrupted system call), and EIO (I/O error while trying to talk
to the firmware).

Features not yet implemented by the driver return ENOSYS.

hwmon device attribute pwm1_enable:
	0: PWM offline (fan is set to full-speed mode)
	1: Manual PWM control (use pwm1 to set fan level)
	2: Hardware PWM control (EC "auto" mode)
	3: reserved (Software PWM control, not implemented yet)

	Modes 0 and 2 are not supported by all ThinkPads, and the
	driver is not always able to detect this.  If it does know a
	mode is unsupported, it will return -EINVAL.

hwmon device attribute pwm1:
	Fan level, scaled from the firmware values of 0-7 to the hwmon
	scale of 0-255.  0 means fan stopped, 255 means highest normal
	speed (level 7).

	This attribute only commands the fan if pmw1_enable is set to 1
	(manual PWM control).

hwmon device attribute fan1_input:
	Fan tachometer reading, in RPM.  May go stale on certain
	ThinkPads while the EC transitions the PWM to offline mode,
	which can take up to two minutes.  May return rubbish on older
	ThinkPads.

hwmon driver attribute fan_watchdog:
	Fan safety watchdog timer interval, in seconds.  Minimum is
	1 second, maximum is 120 seconds.  0 disables the watchdog.

To stop the fan: set pwm1 to zero, and pwm1_enable to 1.

To start the fan in a safe mode: set pwm1_enable to 2.  If that fails
with EINVAL, try to set pwm1_enable to 1 and pwm1 to at least 128 (255
would be the safest choice, though).


EXPERIMENTAL: WAN
-----------------

procfs: /proc/acpi/ibm/wan
sysfs device attribute: wwan_enable

This feature is marked EXPERIMENTAL because the implementation
directly accesses hardware registers and may not work as expected. USE
WITH CAUTION! To use this feature, you need to supply the
experimental=1 parameter when loading the module.

This feature shows the presence and current state of a W-WAN (Sierra
Wireless EV-DO) device.

It was tested on a Lenovo Thinkpad X60. It should probably work on other
Thinkpad models which come with this module installed.

Procfs notes:

If the W-WAN card is installed, the following commands can be used:

	echo enable > /proc/acpi/ibm/wan
	echo disable > /proc/acpi/ibm/wan

Sysfs notes:

	If the W-WAN card is installed, it can be enabled /
	disabled through the "wwan_enable" thinkpad-acpi device
	attribute, and its current status can also be queried.

	enable:
		0: disables WWAN card / WWAN card is disabled
		1: enables WWAN card / WWAN card is enabled.

	Note: this interface will be probably be superseeded by the
	generic rfkill class, so it is NOT to be considered stable yet.

Multiple Commands, Module Parameters
------------------------------------

Multiple commands can be written to the proc files in one shot by
separating them with commas, for example:

	echo enable,0xffff > /proc/acpi/ibm/hotkey
	echo lcd_disable,crt_enable > /proc/acpi/ibm/video

Commands can also be specified when loading the thinkpad-acpi module,
for example:

	modprobe thinkpad_acpi hotkey=enable,0xffff video=auto_disable

Enabling debugging output
-------------------------

The module takes a debug parameter which can be used to selectively
enable various classes of debugging output, for example:

	 modprobe ibm_acpi debug=0xffff

will enable all debugging output classes.  It takes a bitmask, so
to enable more than one output class, just add their values.

	Debug bitmask		Description
	0x0001			Initialization and probing
	0x0002			Removal

There is also a kernel build option to enable more debugging
information, which may be necessary to debug driver problems.

The level of debugging information output by the driver can be changed
at runtime through sysfs, using the driver attribute debug_level.  The
attribute takes the same bitmask as the debug module parameter above.

Force loading of module
-----------------------

If thinkpad-acpi refuses to detect your ThinkPad, you can try to specify
the module parameter force_load=1.  Regardless of whether this works or
not, please contact ibm-acpi-devel@lists.sourceforge.net with a report.


Sysfs interface changelog:

0x000100:	Initial sysfs support, as a single platform driver and
		device.
0x000200:	Hot key support for 32 hot keys, and radio slider switch
		support.
0x010000:	Hot keys are now handled by default over the input
		layer, the radio switch generates input event EV_RADIO,
		and the driver enables hot key handling by default in
		the firmware.

0x020000:	ABI fix: added a separate hwmon platform device and
		driver, which must be located by name (thinkpad)
		and the hwmon class for libsensors4 (lm-sensors 3)
		compatibility.  Moved all hwmon attributes to this
		new platform device.

0x020100:	Marker for thinkpad-acpi with hot key NVRAM polling
		support.  If you must, use it to know you should not
		start an userspace NVRAM poller (allows to detect when
		NVRAM is compiled out by the user because it is
		unneeded/undesired in the first place).
0x020101:	Marker for thinkpad-acpi with hot key NVRAM polling
		and proper hotkey_mask semanthics (version 8 of the
		NVRAM polling patch).  Some development snapshots of
		0.18 had an earlier version that did strange things
		to hotkey_mask.